The present invention relates to a technique for power supply to semiconductor integrated circuit devices, and more particularly to a technique that can be effectively applied to power supply to semiconductor integrated circuit devices provided with nonvolatile memories.
Recently, in the field of control technology for vehicle-mounted devices, a shift to a high speed and reliable Controller Area Network (CAN) is making progress, and the needs are rising for microcomputers having built-in flash memories, which permit ready rewriting of control programs and data, in order to accelerate the development and improvement of CAN-compatible devices.
A semiconductor integrated circuit device for such purposes usually derives power supply from a single line voltage of around 5 V. On the other hand, the operating voltage for semiconductor integrated circuit devices is gradually reduced along with the miniaturization of semiconductor devices. A nonvolatile memory would operate on 3.3 V, and an internal logic element such as a CPU, on 1.9 V.
In this context, in a semiconductor integrated circuit device, a line voltage of around 5 V supplied from a power supply circuit provided within the semiconductor integrated circuit device is stepped down to generate line voltages of around 3.3 V and 1.9 V, which are supplied as operating line voltages.
According to the present inventors' studies, in order to generate two line voltages (around 1.9 V and around 3.3 V) from a single power supply (around 5 V) from outside, it is conceivable as described in Patent Reference 1 to generate first the line voltage of around 3.3 V by stepping down the single power supply from outside, and then further stepping down that stepped-down 3.3 V power supply to around 1.9 V, or first to step down the single power supply from outside to generate a line voltage of around 1.9 V and then to generate a line voltage of around 3.3 V by stepping up that line voltage of around 1.9 V.
On the other hand, Patent Reference 2 discloses a technique by which 1.8 V for internal power supply is generated by stepping down, with a level shifter, an external power supply of relatively high level of 3.3 V, for instance, as the operating voltage.
[Patent Reference 1] Japanese Unexamined Patent Publication No. 2002-135104.
[Patent Reference 2] WO 00/46809